Your use is correct in formal or rhetorical writing, but not in a news article. (In fact, in a news article about an actual incident where the sex of the child is unknown, using ‘he’ could be a big and confusing problem, especially in today’s atmosphere.)
I remain in my conviction that the journalist was using the correct, ages-old form in the article; and was not kowtowing to contemporary thought about ‘gender language’.
Good Night!
I would not advocate “he” in this instance. In this case, with a specific person whose sex is unknown, I would simply go with “the child.”